CPU turbo mode frequency issue with Kernel 3.11 under Saucy 13.10 (Intel I7)

Hi,

I am opening this bug because i'm suspecting my processor not to run under good frequencies under 13.10 with default kernel 3.11.

My computer is an Asus UX52VS running in Intel i7: Intel Core i7-3537U (See http://www.cpu-world.com/CPUs/Core_i7/Intel-Core%20i7-3537U%20Mobile%20processor%20-%20AV8063801119700.html)

It's normal frequency is 2 Ghz with a turbo mode up to 2,9 Ghz in case of CPU Load.

When running Kernel 3.11, cpufreq-info gives me following informations:

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to <email address hidden>, please.
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 775 MHz - 2.50 GHz
  available frequency steps: 2.50 GHz, 2.50 GHz, 2.40 GHz, 2.20 GHz, 2.10 GHz, 2.00 GHz, 1.90 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz, 800 MHz, 775 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 775 MHz and 2.00 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 2.50 GHz (asserted by call to hardware).
  cpufreq stats: 2.50 GHz:-nan%, 2.50 GHz:-nan%, 2.40 GHz:-nan%, 2.20 GHz:-nan%, 2.10 GHz:-nan%, 2.00 GHz:-nan%, 1.90 GHz:-nan%, 1.70 GHz:-nan%, 1.60 GHz:-nan%, 1.50 GHz:-nan%, 1.30 GHz:-nan%, 1.20 GHz:-nan%, 1.10 GHz:-nan%, 1000 MHz:-nan%, 800 MHz:-nan%, 775 MHz:-nan% (582)
analyzing CPU 1:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 1
  CPUs which need to have their frequency coordinated by software: 1
  maximum transition latency: 10.0 us.
  hardware limits: 775 MHz - 2.50 GHz
  available frequency steps: 2.50 GHz, 2.50 GHz, 2.40 GHz, 2.20 GHz, 2.10 GHz, 2.00 GHz, 1.90 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz, 800 MHz, 775 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 775 MHz and 2.00 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 2.50 GHz (asserted by call to hardware).
  cpufreq stats: 2.50 GHz:-nan%, 2.50 GHz:-nan%, 2.40 GHz:-nan%, 2.20 GHz:-nan%, 2.10 GHz:-nan%, 2.00 GHz:-nan%, 1.90 GHz:-nan%, 1.70 GHz:-nan%, 1.60 GHz:-nan%, 1.50 GHz:-nan%, 1.30 GHz:-nan%, 1.20 GHz:-nan%, 1.10 GHz:-nan%, 1000 MHz:-nan%, 800 MHz:-nan%, 775 MHz:-nan% (958)
analyzing CPU 2:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 2
  CPUs which need to have their frequency coordinated by software: 2
  maximum transition latency: 10.0 us.
  hardware limits: 775 MHz - 2.50 GHz
  available frequency steps: 2.50 GHz, 2.50 GHz, 2.40 GHz, 2.20 GHz, 2.10 GHz, 2.00 GHz, 1.90 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz, 800 MHz, 775 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 775 MHz and 2.00 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 2.50 GHz (asserted by call to hardware).
  cpufreq stats: 2.50 GHz:-nan%, 2.50 GHz:-nan%, 2.40 GHz:-nan%, 2.20 GHz:-nan%, 2.10 GHz:-nan%, 2.00 GHz:-nan%, 1.90 GHz:-nan%, 1.70 GHz:-nan%, 1.60 GHz:-nan%, 1.50 GHz:-nan%, 1.30 GHz:-nan%, 1.20 GHz:-nan%, 1.10 GHz:-nan%, 1000 MHz:-nan%, 800 MHz:-nan%, 775 MHz:-nan% (439)
analyzing CPU 3:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 3
  CPUs which need to have their frequency coordinated by software: 3
  maximum transition latency: 10.0 us.
  hardware limits: 775 MHz - 2.50 GHz
  available frequency steps: 2.50 GHz, 2.50 GHz, 2.40 GHz, 2.20 GHz, 2.10 GHz, 2.00 GHz, 1.90 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz, 800 MHz, 775 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 775 MHz and 2.00 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 2.00 GHz (asserted by call to hardware).
  cpufreq stats: 2.50 GHz:-nan%, 2.50 GHz:-nan%, 2.40 GHz:-nan%, 2.20 GHz:-nan%, 2.10 GHz:-nan%, 2.00 GHz:-nan%, 1.90 GHz:-nan%, 1.70 GHz:-nan%, 1.60 GHz:-nan%, 1.50 GHz:-nan%, 1.30 GHz:-nan%, 1.20 GHz:-nan%, 1.10 GHz:-nan%, 1000 MHz:-nan%, 800 MHz:-nan%,

I don't understand why "frequency should be within 775 MHz and 2.00 GHz." ?

As far as i can see with various tools, the current frequency nevers goes up to 2 Ghz which is far away from the turbo hardware limit...

Another tool says almost the same:

analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 775 MHz - 2.50 GHz
  available frequency steps: 2.50 GHz, 2.50 GHz, 2.40 GHz, 2.20 GHz, 2.10 GHz, 2.00 GHz, 1.90 GHz, 1.70 GHz, 1.60 GHz, 1.50 GHz, 1.30 GHz, 1.20 GHz, 1.10 GHz, 1000 MHz, 800 MHz, 775 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance
  current policy: frequency should be within 775 MHz and 2.00 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.60 GHz.
  cpufreq stats: 2.50 GHz:-nan%, 2.50 GHz:-nan%, 2.40 GHz:-nan%, 2.20 GHz:-nan%, 2.10 GHz:-nan%, 2.00 GHz:-nan%, 1.90 GHz:-nan%, 1.70 GHz:-nan%, 1.60 GHz:-nan%, 1.50 GHz:-nan%, 1.30 GHz:-nan%, 1.20 GHz:-nan%, 1.10 GHz:-nan%, 1000 MHz:-nan%, 800 MHz:-nan%, 775 MHz:-nan% (3159)
  boost state support:
    Supported: yes
    Active: yes
    25500 MHz max turbo 4 active cores
    25500 MHz max turbo 3 active cores
    25500 MHz max turbo 2 active cores
    25500 MHz max turbo 1 active cores

Running under very high CPU load, i can see using turbostat:

cor CPU %c0 GHz TSC SMI %c1 %c3 %c6 %c7 CTMP PTMP %pc2 %pc3 %pc6 %pc7 Pkg_W Cor_W GFX_W
         84.87 2.88 2.49 0 15.13 0.00 0.00 0.00 84 84 0.00 0.00 0.00 0.00 16.07 11.10 0.19
  0 0 78.49 2.88 2.50 0 21.51 0.00 0.00 0.00 81 84 0.00 0.00 0.00 0.00 16.07 11.10 0.19
  0 2 88.18 2.88 2.50 0 11.81
  1 1 80.60 2.88 2.49 0 19.40 0.00 0.00 0.00 84
  1 3 92.23 2.88 2.49 0 7.77
cor CPU %c0 GHz TSC SMI %c1 %c3 %c6 %c7 CTMP PTMP %pc2 %pc3 %pc6 %pc7 Pkg_W Cor_W GFX_W
         85.58 2.89 2.49 0 14.39 0.03 0.00 0.00 84 84 0.00 0.00 0.00 0.00 16.20 11.25 0.17
  0 0 92.59 2.89 2.49 0 7.36 0.05 0.00 0.00 82 84 0.00 0.00 0.00 0.00 16.20 11.25 0.17
  0 2 78.25 2.89 2.49 0 21.70
  1 1 85.93 2.89 2.49 0 14.07 0.00 0.00 0.00 84
  1 3 85.56 2.89 2.49 0 14.44
cor CPU %c0 GHz TSC SMI %c1 %c3 %c6 %c7 CTMP PTMP %pc2 %pc3 %pc6 %pc7 Pkg_W Cor_W GFX_W
         84.59 2.89 2.49 0 15.41 0.00 0.00 0.00 83 83 0.00 0.00 0.00 0.00 16.01 11.14 0.11
  0 0 95.59 2.89 2.49 0 4.41 0.00 0.00 0.00 81 83 0.00 0.00 0.00 0.00 16.01 11.14 0.11
  0 2 62.31 2.88 2.49 0 37.69
  1 1 87.46 2.89 2.49 0 12.54 0.00 0.00 0.00 83
  1 3 93.02 2.89 2.49 0 6.98

But, when using the last Kernel 3.12 (rc7) revision what i see is completely different!

With running kernel 3.12:

cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to <email address hidden>, please.
analyzing CPU 0:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 0.97 ms.
  hardware limits: 800 MHz - 3.10 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 3.10 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 2.90 GHz (asserted by call to hardware).
analyzing CPU 1:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 1
  CPUs which need to have their frequency coordinated by software: 1
  maximum transition latency: 0.97 ms.
  hardware limits: 800 MHz - 3.10 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 3.10 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 2.90 GHz (asserted by call to hardware).
analyzing CPU 2:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 2
  CPUs which need to have their frequency coordinated by software: 2
  maximum transition latency: 0.97 ms.
  hardware limits: 800 MHz - 3.10 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 3.10 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 2.90 GHz (asserted by call to hardware).
analyzing CPU 3:
  driver: intel_pstate
  CPUs which run at the same hardware frequency: 3
  CPUs which need to have their frequency coordinated by software: 3
  maximum transition latency: 0.97 ms.
  hardware limits: 800 MHz - 3.10 GHz
  available cpufreq governors: performance, powersave
  current policy: frequency should be within 800 MHz and 3.10 GHz.
                  The governor "powersave" may decide which speed to use
                  within this range.
  current CPU frequency is 2.90 GHz (asserted by call to hardware).

As you can see the 2 kernels does not seem to use the same driver, intel_pstate for Kernel 3.12 and acpi-cpufreq for Kernel 3.11.

Reported speed are correct for Kernel 3.12 and the system works much better and more fluent, i can really feal the difference.

Frequency tools report a good frequency, going up to 3 Ghz under high CPU Load. (under Kernel 3.12 i can't use turbostat, gives me an error :
turbostat not found for kernel 3.12.0-031200rc7
You may need to install linux-tools-3.12.0-031200rc7-generic
)

So what does that mean ?
Is a 3.11 kernel unable to manage correctly that kind of processor ? Anything else to do to correct that ?

Many people have that kind of modern processor in recent laptops, i guess many shall be interested in...

Thank you in advance for your help !